Paramount ME concrete pier

All,My college will be buying a paramount ME in about two years, and we are in the process of designing an observatory for it. Payload will be an 12" Meade SCT and later on, probably a larger-aperture RC. We are looking for advice on a concrete pier. The pier top will be at least 8 feet off the ground.

It seems like 12" concrete columns are popular, made from the standard sonotube. Is there any advantage to instead having a pier that is cone-shaped instead of cylindrical? We are looking for maximum stability and minimization of vibrations from surrounding area (isn't everyone?)

I can't help you with some of that, but I went to a localbuilding supply and got a 14 inch x 10 foot sonotube thatwas substantially more durable than the sonotubes soldat the local Home Depot/Lowes for my ME. With the 14 inchwidth, the heavy duty Bisque pier adapter works like a charm.

You'll want something like a 4' cube as a foundation. You should consider the need for drainage of your foundation if ground water is a problem. I don't know about a cone, other than it won't be easy to fabricate a form.

I just built as pier for my paramount mx.I used the sonotube.You have to bury the pier to at least the frost line to prevent heaving.My frost line was 36 inches below ground so I went 48 inches deep with mine.You can find out the frost line for your area by going online. i found someone that had made piers for streetlights so he knew about the depth etc....

Don't forget to add in rebar, I found out how much strength that adds when I had to take a pier down when I moved

Definitely it's good to try to get a tougher sonotube material. To get the bubbles out of my 8' pier (4' below ground, 4 above) I slapped the sides a lot with my hands and rhythmically squeezed it (the concrete was pretty wet). It worked well to get out most of the air, but by the end of it the sonotube cardboard was very much saturated with water. The whole thing started to lose integrity and crumple on one side at the bottom - I had to support it with some wood to keep it steady until it dried. I haven't measured, but I think it also got a bit widened on the top as well due to my abuse, so it ended up like a reverse tapered cylinder. Still, in the end it does the job.

If you really want the concrete to settle well, I know you can rent vibrating tools that are meant to be inserted into the concrete for a very short time, shouldn't harm the sonotube at all.

Does the scool have a CE program? I had one design my pier and it also included soil analysis and the 'footing' design(below ground component of pier). What came up with was a sort of Eiffel tower of rebar that began in the pier footing and continued up the pier column. This made it near impossible to vibrate internally in the wet mix so was done from the sides. At any rate if it's for an institution I'd get someone with a stamp to do the design - might even be a requirement depending on their insurance and building codes. Best luck on the obs project !

No CE program here, but we do have some knowledgeable people who can do some of the analysis you mention. I'm trying to compile base-line best practices to make sure we're not grossly over or under building. Thanks for the ideas, everyone!

I use a length of rebar by driving it up and down in the tube. Kind of like churning water. Works well enough for concrete mixed properly. Mistake is often made to use too much water in an attempt to speed/ease mixing and finishing. In the end you'll weaken the mix. I go by the 1-2-3 rule. One part portland, two sand and three stone with a ratio by weight of 0.4 water to portland. So an 80 pound bag of portland requires 32 pounds of water or a little less then 3 gallons. My mixer handles about a third of a bag of portland per batch, so that's just one gallon. This is pretty stiff. If you get your concrete mixed commercially they can add plasticizers or super-plasticizers to ease handling.

If you are in a northern area where there is significant ground freeze, a tapered pier will be more immune to being moved/lifted by the frost than a straight one.If you check at better lumber yards or masonry supply houses, there are a range of one-piece heavy-duty plastic pier forms that look somewhat like upside-down champagne glasses, that being smooth and black, make attractive finished piers. One of them over a big footing poured right into a carefully dug hole will yield a substantial and stable scope base. Also, consider inserting a piece or two of plastic conduit in the pier before the pour for wires going to the scope. The conduits could even extend under the floor to a box mounted on a side wall......Russ